Ignore AltGr keystrokes in Ctrl+Alt keyboard shortcuts (#825)

* Ignore AltGr keystrokes in Ctrl+Alt keyboard shortcuts

Browsers report AltGr (right Alt on AZERTY/QWERTZ and most non-US
layouts, used to type @ # { } [ ] | \ and the euro sign) as
ctrlKey+altKey. The default keybinds map destructive actions to
Ctrl+Alt+<letter> (delete_session, new_session, incognito,
open_calendar), so a non-US user typing a special character could
silently fire them.

Guard the shortcut matcher, the editor keydown handler, and the rebind
capture with getModifierState('AltGraph'), which is true for AltGr but
false for a genuine left Ctrl+Alt. macOS is excluded: there the Option
key legitimately sets AltGraph and there is no AltGr/Ctrl+Alt collision
to guard against, so the guard would otherwise break Ctrl+Option /
Cmd+Option shortcuts (notably in Firefox).

The detection lives in one place — isAltGrEvent / IS_MAC in
static/js/platform.js — and all three call sites route through it, so the
guards can't drift apart.

The editor handler only skips the Ctrl+Alt chord block, so layout
shortcuts reachable via AltGr (e.g. [ ] brush size = AltGr+5/+8 on
AZERTY) keep working.

* Require Ctrl+Alt for the AltGr guard and consolidate keybind test marks

isAltGrEvent now also checks ctrlKey+altKey so it only suppresses the
"AltGr reported as Ctrl+Alt" collision; an event asserting AltGraph on
its own (a Linux ISO_Level3_Shift layout, a stray modifier) is left
alone. Pin it with test_isaltgr_false_when_altgraph_set_but_not_ctrl_alt.

Collapse the 12 per-test node skipif marks into one module-level
pytestmark, and note in platform.js why IS_MAC intentionally covers
iPad/iPhone and mirrors the isMac checks in calendar.js / sessions.js.

static/js/editor/keyboard-shortcuts.js

@@ -50,6 +50,7 @@
  * }} deps
  */
 import { state } from './state.js';
+import { isAltGrEvent } from '../platform.js';
 
 export function wireKeyboardShortcuts(deps) {
   const {
@@ -79,7 +80,11 @@ export function wireKeyboardShortcuts(deps) {
       return;
     }
     if (e.key === 'Escape') return;
-    if (e.ctrlKey || e.metaKey) {
+    // Skip the Ctrl+Alt editor chords for an AltGr keystroke (see platform.js);
+    // only the chord block is skipped, so the layout-character handlers below
+    // still act — AltGr+5 / AltGr+8 stay as the [ ] brush-size shortcut on
+    // AZERTY / QWERTZ.
+    if ((e.ctrlKey || e.metaKey) && !isAltGrEvent(e)) {
       if (e.key === 'z') { e.preventDefault(); if (e.shiftKey) redo(); else undo(); }
       // Ctrl+Shift+D = Deselect: clears the wand selection (and
       // lasso if active) without affecting layers.

static/js/keyboard-shortcuts.js

@@ -2,6 +2,8 @@
 // Keyboard Shortcuts — dynamic keybinds
 // ============================================
 
+import { IS_MAC, isAltGrEvent } from './platform.js';
+
 const _defaultKeybinds = {
   search: 'ctrl+k', toggle_sidebar: 'ctrl+alt+b', new_session: 'ctrl+alt+n',
   fav_session: 'ctrl+alt+f', delete_session: 'ctrl+alt+d',
@@ -13,8 +15,11 @@ const _defaultKeybinds = {
   open_notes: '', open_tasks: '', open_theme: '',
 };
 
-function _matchesCombo(e, combo) {
+export function _matchesCombo(e, combo, isMac = IS_MAC) {
   if (!combo) return false;
+  // Drop AltGr keystrokes so typing characters on non-US layouts can't fire a
+  // Ctrl+Alt shortcut — e.g. the destructive delete_session. See platform.js.
+  if (isAltGrEvent(e, isMac)) return false;
   const parts = combo.split('+');
   const needCtrl = parts.includes('ctrl');
   const needAlt = parts.includes('alt');

static/js/platform.js

@@ -0,0 +1,47 @@
+// ============================================
+// Platform detection + AltGr-keystroke helper
+// ============================================
+// Shared by the keybind code: root keyboard-shortcuts.js, the editor's
+// keyboard-shortcuts.js, and settings.js. Single source of truth so the three
+// guards can't drift.
+
+// AltGr (right Alt on AZERTY/QWERTZ and most non-US layouts, used to type
+// @ # { } [ ] | \ and €) is reported by browsers as Ctrl+Alt. macOS is the
+// exception: there the Option key — a normal part of Mac shortcuts — also sets
+// the AltGraph modifier state, so it must NOT be treated as AltGr.
+//
+// IS_MAC covers all Apple platforms, iPad/iPhone included: a Magic Keyboard's
+// Option key sets AltGraph exactly like a Mac's, so they need the same carve-out
+// — narrowing to macOS-only would re-break them. The name and the
+// /Mac|iPhone|iPad/ test deliberately mirror the existing isMac checks in
+// calendar.js and sessions.js; this is their single shared source of truth.
+export const IS_MAC =
+  /Mac|iPhone|iPad/.test((typeof navigator !== 'undefined' && navigator.platform) || '') ||
+  /Mac/.test((typeof navigator !== 'undefined' && navigator.userAgent) || '');
+
+// True when `e` is an AltGr keystroke we should ignore for Ctrl+Alt shortcut
+// purposes. getModifierState('AltGraph') is true for AltGr but false for a
+// genuine left Ctrl+Alt, so real shortcuts still work. Always false on macOS,
+// where Option legitimately sets AltGraph.
+//
+// We also require ctrlKey+altKey: the collision we defend against is precisely
+// "AltGr reported AS Ctrl+Alt", so an event that asserts AltGraph WITHOUT
+// presenting as Ctrl+Alt (a Linux ISO_Level3_Shift layout, a stray modifier
+// state) is left alone instead of being swallowed.
+//
+// Trade-off: on Windows AltGr *is* Ctrl+right-Alt, so a deliberate
+// Ctrl+Alt+<char> shortcut typed via AltGr is unreachable too — accepted; use
+// the left Ctrl+Alt.
+//
+// NOTE: the AltGr -> AltGraph mapping is taken from the UI Events spec / MDN,
+// not proven by our tests. Older Firefox and some Linux setups historically did
+// not report AltGraph; where a browser sets ctrlKey+altKey without it this
+// guard is simply a no-op (the pre-fix behaviour) rather than a regression.
+export function isAltGrEvent(e, isMac = IS_MAC) {
+  return (
+    !isMac &&
+    !!e.ctrlKey &&
+    !!e.altKey &&
+    !!(e.getModifierState && e.getModifierState('AltGraph'))
+  );
+}

static/js/settings.js

@@ -6,6 +6,7 @@ import searchModule from './search.js';
 import { makeWindowDraggable } from './windowDrag.js';
 import { clearDockSide } from './modalSnap.js';
 import { sortModelIds } from './modelSort.js';
+import { isAltGrEvent } from './platform.js';
 
 let initialized = false;
 let modalEl = null;
@@ -1710,6 +1711,10 @@ function _formatKeyCaps(combo) {
 }
 
 function _comboFromEvent(e) {
+  // Drop a stray AltGr keystroke (e.g. AltGr+E to type €) so it isn't recorded
+  // as a bogus ctrl+alt+<char> binding — onKey ignores empty combos. See
+  // platform.js for the macOS carve-out and Windows trade-off.
+  if (isAltGrEvent(e)) return '';
   const parts = [];
   if (e.ctrlKey || e.metaKey) parts.push('ctrl');
   if (e.altKey) parts.push('alt');